Multisection semiconductor lasers for optical microwave generation have been fabricated that consist of a loss-coupled distributed feedback (LC-DFB), a phase control, and an amplifier section. High-frequency self-pulsations are generated according to the concept of a single-mode laser with short optical feedback. The effect of the optical feedback via the phase control and the amplifier section on the self-pulsation is apparently shown as a result of the superior single-mode characteristic of the LC-DFB section. Continuous frequency tuning is achieved in the range of 17-35 GHz.

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We demonstrated 10.7 Gb/s reflective electroabsorption modulator monolithically integrated with semiconductor optical amplifier (REAM-SOA) using simplified fabrication process. Good performance at 10.7 Gb/s was obtained with an extinction ratio of > 10 dB and a power penalty of < 1 dB at a 10(-9) bit error rate (BER) up to 20 km transmission. The device operated over a 50 nm spectral range within 1 dB received power variation at a 10(-9) BER.

We demonstrated two-section reflective semiconductor optical amplifier (RSOA) with dramatic improvement of small-signal modulation bandwidth above 10 GHz as colorless source for wavelength division multiplexed-passive optical network (WDM-PON). The device provides the fiber-to-fiber gain of 22.8 dB, 3-dB amplified spontaneous emission (ASE) bandwidth of 30 nm, and ripple of 1.5 dB. Good performance at 2.5 Gbps was obtained with an extinction ratio of 8 dB and a power penalty of 2 dB at a 10(-9) bit error rate (BER) up to 20 km transmission.

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We present fabrication results of a planar-buried-heterostructure (PBH)-type reflective semiconductor optical amplifier (R-SOA). Active and passive waveguides forming R-SOA were integrated by butt-coupling. The optical gain and 3 dB amplified spontaneous emission (ASE) bandwidth were about 25 dB and 35 nm, respectively. The polarization-dependent gain (PDG) was about 0.8 dB. We could obtain a clearly opened eye diagram under 2.5 Gbps direct modulation. In a bit-error-rate (BER) test, the receiver sensitivity and power penalty after 20 km transmission were about À27 dBm and 2 dB, respectively.